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power supply in base amp problems

B

bettyeboop

Member
Sep 12, 2007
48
0
16
deep south
I am trying to get the voltage down on an unregulated power supply.....it is frying pills because it is doing 22 volts at key up and goes down only to 16.

I have tried using a five watt resistor of different values both on the ac side(pri and sec) and dc side.....could some give me some direction??????????????

I have noticed that the voltage always goes up after going through the diode rectifier.
I am using two four pin rectifiers with a resistor and cap across the dc pins.

I would be willing to help anyone build your own power supply ......just let me get this last problem figured out. I have one that is 125-150 amps using two large transformers and a bank of caps..

oh yea this amp has two 2879's.

thanks ,

davis
 

He did say it is unregulated. That is the problem. Any dropping resistor that you use would have to handle a LOT of power no matter where it is placed in the circuit,primary or secondary. The formula for determining power is volts dropped multiplied by the current drawn. If the amp draws 25 amps and you need to drop 3 volts then the resistor needs to be able to handle AT LEAST 75 watts and that would be pushing it to its limits.The other problem with unregulated power supplies is that if used on SSB,the voltage swings all over the place with changes in load current that occurs with modulation. In short,there is no easy and cheap method to solve your problem except sell the power supply and buy a heavy duty regulated one.
 
no carl there is no regulator......Is there a regulator board you can build or buy? My dave made base box is not regulated and has worked fine for years. It is a simple trans. , rectifier, and cap.

What about a coil of some type. I just can't give up on this. A regulated power supply cost too much for this amp. I use a 25 amp regulated on my bench in parallel with a gell battery on the floor.

I also built a 125 amp power supply with two transformers and 12- 22000 uf caps and 8 rectifiers. It works great and the voltage is 16 volts but goes down some at key up. I had to buy a 400 amp dc meter to see about what this beast is doing. After being successful on the big one you can understand why I can't give up on this little one.
 
L1 you can receive PM's , your box is only allowed so many , when it fills up , you need to empty it , then you can receive so many more before it fills back up and you would need to empty it again. Unless IM missing something here ? I think mine first read 125 now it reads 10 , looks like I have been (or we) have been branded to so many without money membership. What would be the need to save them anyway ? I would think 10 would be more then enough. Maybe I am missing something here ?
 
l=1,
The trans I have used before is numbered 430-9001. I have three of these in my base amp. I would love to find a supplier of these or similar. They are very reasonable.

I bought two off of ebay that were 50 amp 16 volt sec. They work great.

I have had good luck using multiple trans as long as they are the same specs.


I just need a good supplier that stocks such as this.

thanks davis
 
Since you are doing AC/DC conversion why not look at using scr's to regulate the power supply? I know it is still a little cost but not near that of a linear supply or switching and as far as noise goes it is very low i.e. not noticable. I will have to dig around and see if I can find some of my old scribblings.

I just thought I would bring it up since some do not know of this method of regulating, do some "googling".
 
thanks.....I have been swamped with radio work...putting up a tower....etc.....

thanks for all the good help. I went to the jackson hamfest and talked to a electronics teacher from alabama. He gave me the numbers of a regulator , small transistor and the power transistors for a regulated supply.....just have not done it yet....if anyone wants the numbers I will post them after I build it and it works ok.

thanks so much
 
dtb I am going to look into your schematic too....how much amperage will this handle. and do you just parallel the circuit to get the amprage of your transformer.

I need to send you my personal ranger 2950.....it lights up but no key up and no recieve...a little noise from fm........three sets of jumpers and I cant get 11 meters to show either. I have pushed lock and done all that is supposed to work. the board number is elk 295013q
i think this is right. the radio is in the other room it is not a dx model and there is no blue dot on the back anywhere.

can you give me advise or just give me your address with aprox turnaround.

thanks so much,
galyn davis

galyndavis@yohoo.com
 

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